Cyril and Methodius were born in Thessaloniki and were sons of a prominent Christian family with seven children. Their father, Leo was a droungarios of the Byzantine theme of Thessaloniki. Cyril, the youngest one, was born in 826-827, while Methodius in 815. Their high education and prominent descent brought them close to the emperor and opened the path for a great career.
Methodius attended the education reserved for those who aimed positions in the higher administrative hierarchy of Byzantium and was put in charge of the Slavic theme, where he became familiar with the Slavic language. After serving for a few years he quitted and retreated to a monastery in Olympus, Bithynia.
Cyril displayed a unique tendency in learning from the early beginning. At the age of 14 he knew by heart the writings of Gregorius the Theologian. He studied, among other subjects, mathematics and philosophy, and showed a remarkable skill in learning foreign languages. Due to these skills, he was known as “the Philosopher” and was given the opportunity to become a high ranking empire official.
Theoktistos was deeply disappointed by Cyril’s denial to wed his adopted daughter, but due to the fact that he didn’t want to alienate him, he offered him the position of the Patriarch’s Bookkeeper at the temple of Agia Sofia in Constantinople. He was ordained as a deacon probably in 850, while the following year he was accepted as a professor of philosophy at the University of Constantinople.